The Earth's climate is changing and there is a consensus that the dominant cause of this is emissions of greenhouse gases (GHG) like CO2 by mankind. Computer climate models are predicting that temperatures will be rising over 20-50 years given GHG increases.
Climate models, however, are far from perfect. The biggest uncertainty in computer models today is how they simulate the physics/chemistry of what is called cloud feedback. Generally, as CO2 GHG warms the planet, by increasing the greenhouse effect, will the planet get more clouds, less clouds, or different clouds? Will the cloud changes enhance or reduce global warming (i.e. because clouds both cool the Earth by reflecting sunlight and warm by trapping infra-red in space)? Presently, climatologists are not sure whether the net effect is to enhance positive feedback or reduce negative feedback, the cloud coverage and how much the cloud feedbacks will amplify the warming.
In order to reduce the total uncertainty range in climate change predictions there is a need to ensure the models are correctly simulating how clouds are responding with feedback and hence forcing the climate in one course or another.
It will be appreciated, however, that the size of cloud feedback is very small. For example, it is on the order of less than watt/meter2 change of energy over only a 1° C. temperature change. This means that the sensors observing climate changes over the Earth have to be very stable. Since these sensors are not perfect, they must be calibrated to an absolute accuracy of 0.3% and a calibration stability of 0.1% per decade.
Maintaining calibration of climate data records (CDRS) is challenging due to many reasons. For example, optics can be subject to degradation of up to 30% in the UV, often due to contamination. Many existing instruments do not have stable on-board calibration sources in the UV-visible region and establishing traceability to NIST standards for solar wavelengths is difficult. On-board blackbodies have also been seen to drift in their thermal output to extents not reflected by their temperature sensors.
It will be appreciated that even if a perfect instrument could be launched to monitor the Earth, it would still take nearly two decades to detect the small 0.6% size of cloud feedback. So a launch of a perfect instrument like CLARREO would still not provide an answer before 2040 (CLARREO was a $1 billion mission being designed to make near perfect measurements that was cancelled due to budget cuts).
As will be explained, the present invention provides methods for calibrating existing instruments on-board various satellites that orbit the Earth to measure its albedo and thermal infra-red output to space. The methods of the present invention are inexpensive compared to launching new instruments that are “near perfect.” In addition, by calibrating existing instruments, trends in climate changes may become known within ten years, rather than the thirty years that would be required for the launching of a new instrument (10 years of planning plus 20 years of observable data). By correcting the calibration of an existing instrument, its data may be corrected back into the past to the time of its launch. Thus, 20 years of observable data may be available much sooner.